In general, a steering apparatus is an apparatus through which a driver can freely change a driving direction of a vehicle and also an apparatus supporting the optional change of a rotation center about which a front wheel of a vehicle turns to drive vehicle in a desired direction of a driver.
The steering power generated by the operation of a steering wheel by a driver in the steering apparatus of a vehicle is transferred to a rack pinion mechanism through a steering shaft and finally changes the direction of both wheels.
FIG. 1 is a diagram schematically illustrating a general rack pinion-type steering apparatus for a vehicle.
As shown in FIG. 1, the conventional rack pinion-type steering apparatus includes a steering wheel 100 positioned in a driver's seat, a steering shaft 105 connected to the steering wheel 100, a steering column 103 for fixing the steering shaft to a vehicle body, a gear box 103 including a rack gear 110 and a pinion gear 120 for converting rotation force received from the steering shaft 105 into a linear movement, a rack bar 140 including an inner ball joint 135 at both ends, and a tie rod 150 integrally formed with the inner ball joint 135.
Further, the tie rod 150 is connected with an outer ball joint 155, transfers power to a knuckle 159, and steers a tire 158.
FIG. 2 is a cross-sectional view illustrating a conventional rack bar supporting device.
As shown in FIG. 2, the conventional rack bar supporting device includes a pinion gear 120, a rack bar 140, a support yoke 260, a spring 263, and a yoke plug 265. A rack pinion-type gear box 130 converts rotation force received from a steering shaft (not shown) into a linear movement as described above.
The rack bar 140 is meshed with the pinion gear 120 to convert the rotation movement to the linear movement and includes a device for supporting the rack bar 140 toward the pinion gear 120 in a rear surface thereof so as for the rack bar 140 and the pinion gear 120 to be meshed well with each other.
The device for supporting the rack bar 140 includes a support yoke 260, a spring 263, and a yoke plug 265. The support yoke 260 is positioned in a surface opposite to a surface on which the rack gear 110 (refer to FIG. 1) is formed that is a rear surface of the rack bar 140, and is inserted to a cylinder 250 of the gear box 130 to be movable in a front and rear direction that is vertical with respect to the rack bar 140.
The support yoke 260 is shaped like a cylinder so as to slide in a front and rear direction in the cylinder 250 and a front part being in contact with the rack bar 140 includes a groove shaped like a half circle so as to be in close contact with the rear surface of the rack bar 140.
Further, a spring 263 is arranged in a rear area of the support yoke 260 so as for the rack bar 140 and the pinion gear 120 to be in close contact with each other to efficiently transfer power so that it pushes the support yoke 260 with a uniform pressure to compensate for the clearance generated between the rack bar 140 and the pinion gear 120.
Such a support yoke 260 slides relative to and rubs with the rear surface of the rack bar 140 and is made of plastic softer than the conventional rack bar 140 so as to prevent the rack bar 140 from being worn or the generation of noise caused by friction.
The spring 263 received in a spring groove 220 applies pressure so as for the support yoke 260 to come into close contact with the rack bar 140 and uses a general coil spring. The yoke plug 265 is positioned in a rear surface of the spring 263 to support the spring 263.
The yoke plug 265 supports the spring 263 to apply pressure to the support yoke 260. The yoke plug 265 generally includes a screw thread formed with a concave facet to be assembled with the gear box 130 and a lock nut 240 including a screw thread formed with a concave facet. The yoke plug 265 includes a tool groove 230 for inserting a wrench in a rear surface thereof.
If the rack bar is in contact with the support yoke supporting the rack bar to experience certain endurance, the above conventional rack bar supporting device generates the rattle noise due to the clearance caused by the wearing and fails to properly support the rack bar, thereby causing the problem of deterioration of the steering safety.
Further, the displacement of the spring assembled for compensating for the clearance increases as much as the clearance increased during generating the clearance by the wearing of the support yoke so that tension of the spring is deteriorated. As a result, a problem occurs in the structure that if same impulse is applied, noise increases.